The apparatus and method for processing crop residue into more nutritional products generally relates to implements and more specifically to a pressure device that processes agricultural residue.
Since 1980 there have been at least 24 international conferences and workshops in Africa and Asia to consider research and development on crop residues as feed with emphasis on improving their intake and digestibility in ruminant animals. Little practical application has occurred because of difficulties in transporting and storing crop residues and insufficient demonstration of economic benefits from treatment and supplementation. However, as populations increases and the demand for food increases there will be increasing pressure to find ways to balance crop production and animal husbandry.
Crop residue is typically high in fiber (lignocellulosic cell wall constituents) and low in crude protein and energy. It is also not a perfectly homogenous forage. It is mainly composed of cellulose (35-50%), hemicellulose (15-30%), lignin (20-30%), nitrogenous compounds and ash. The exact composition depends on the type and variety of crop residue. Even though crop residue contains enough cellulose to make it an excellent source of dietary energy to ruminates, it is a poor quality feed in its natural state because of low digestibility and protein content, poor palatability and bulkiness.
The search for ways of adding nutritional value to cereal crop residue dates back to the 1930 and 1940's in Germany. During WWI fodder shortages due to the war lead to the development of the Beckmann Method which was practiced on farms to improve the digestibility and intake of crop residue. The Beckmann Method is a practical method of treating crop residue with NaOH and is recognized as a technically viable means of upgrading the feed value of crop residue. The process involves soaking the crop residue in 1.5% solution of NaOH solution at atmospheric temperature and pressure, then draining and washing the crop residue with water to remove the alkali. This treatment results in a wet crop residue with a sodium content of 2%. This method produces a two-fold increase in digestibility of the crop residue. However, the method has several significant disadvantages; it losses about 25% of dry matter, it creates significant waste disposal issues and its economics are not always favorable.
Despite the drawbacks of the Beckmann method many farmers will take their dry crop residue sprinkled or sprayed it with NaOH solution to wet the crop residue to produce a moist material that has a pleasing yellow color and a caustic soda smell. Animals have been shown to eat 10-20% more of this crop residue that untreated crop residue. A variation of this method is the Boliden method developed in Sweden where the crop residue is sprayed using a specially designed apparatus with an alkali solution followed by an acid solution. The saturated crop residue is allowed to stand overnight. The treated crop residue physically resembles the wet treated crop residue but chemically it resembles the dry treated crop residue neutralized with minerals. It has sufficient calcium and phosphorous to eliminate the need for supplements. Both approaches require a degree of sophistication on the part of the farmer to properly treat the crop residue with chemicals and the resulting feed is still lacking in the desirable nutrition needed to sustain a healthy ruminate animal.
Several have tried to improve the NaOH treatment process by using a closed system to eliminate the waste disposal problem. Torgrimsby for example developed a process in which the amount of water added to the system is equal to the amount removed from the crop residue. Three tanks are needed; the first for soaking the crop residue in the NaOH solution (similar to the Beckman method) followed by two rinsing tanks. In the first rinsing tank, the alkali is washed out of the treated crop residue by adding fresh crop residue thus pretreating the new crop residue while increasing the removal of excess NaOH from the treated crop residue. A final washing is performed in the third tank.
Research on the use of ammonia, or NH3, occurred in the mid 1970's. Ammonia, NH3, treatments are less effective than NaOH and requires the crop residue to steep in a closed container in a solution of 30% water and 5% ammonia for 30 days at room temperature. Under these conditions the digestibility of the crop residue has been reported to increase from 29 to 63%. However, waste disposal and processing economics are key draw backs to the adoption of this method.
Mechanical processes such as grinding, chopping, shredding, pelleting, milling and extrusion are all common techniques for reducing the particle size of the crop residue. Generally, coarsely chopped crop residue is the most commonly used method to increase daily intake, improve digestibility and is the most economical approach. However, this treatment is inefficient by it self.
Biological treatment methods with lignolitic mciro-organisms, including bacteria and fungi, and/or enzymic products can be used to break down the bonding structure between cellulose and hemicellulose and lignin in the crop residue, extract and decompose the lignin to release the polysaccharides and oligomers resulting in better access to the processed nutrients of the crop residue for the ruminate micro flora to act upon and improve digestibility. Many factors influence the effectiveness of this approach including selection of the appropriate microorganism, temperature, duration of the fermentation and the quality and composition of the crop residue.
Improving the digestibility and protein content using various techniques have been studied and tried by many researchers. The development of inexpensive, efficient methods of handling and treating crop residue on the farm is of great interest especially in developing areas of Asia and Africa. As populations increase and the demand for food crops increases the pressure on developing livestock feed will continue to increase.
In Ethiopia, for example, which has the largest livestock population in Africa, approximately 26 million head of cattle roam including about 6 million draught oxen. About 80% of these animals are raised in the highlands and are fed, especially in the dry seasons (November to May) by crop residues or cereal crop residues. Some estimates suggest that 40-50% of the livestock feed is composed of cereal crop residue. The animals feed on the crop residues that have either been piled in stacks near the homestead or they eat the residue left in the fields along with standing crop residue.
Farm scale treatment methods or those used by the individual farm require simple and economical processes that any farm with any technical sophistication can implement.